Abstract:

A contrast dye for preparing a lithographic printing plate includes at
least one A, D, and B group wherein A represents a phosphorous containing
group capable of reacting with the surface of a lithographic receiver; D
represents a chromophore group absorbing light between 400 nm and 700 nm;
and B represents an aliphatic group of at least 6 carbon atoms. A
lithographic printing plate includes such a contrast dye.

Claims:

1-13. (canceled)

14. A contrast dye for preparing a lithographic printing plate
comprising:at least one A, D, and B group; whereinA represents a
phosphorous containing group capable of reacting with the surface of a
lithographic receiver;D represents a chromophore group absorbing light
between 400 nm and 700 nm; andB represents an aliphatic group of at least
6 carbon atoms.

15. A contrast dye according to claim 14, wherein the aliphatic group B
contains at least one fluorine atom.

16. A contrast dye according to claim 14, wherein the contrast dye has the
structure AxDyBz wherein x, y, and z are each
independently integers from 1 to 10,000, and the A and B groups are
covalently bonded to the chromophore group D.

17. A contrast dye according to claim 15, wherein the contrast dye has the
structure AxDyBz wherein x, y, and z are each
independently integers from 1 to 10,000, and the A and B groups are
covalently bonded to the chromophore group D.

18. A contrast dye according to claim 16, wherein x and z are each
independently integers from 1 to 8 and y is 1 or 2.

19. A contrast dye according to claim 17, wherein x and z are each
independently integers from 1 to 8 and y is 1 or 2.

20. A contrast dye according to claim 14, wherein the contrast dye has a
polymeric backbone and the groups A, D, and B are covalently bonded to
the polymeric backbone according to one or more structures selected from
the group consisting of AxDyBz, AxDy,
AxBz, DyBz, A, D, and B; wherein x and z are each
independently integers from 1 to 8 and y is 1 or 2.

21. A contrast dye according to claim 15, wherein the contrast dye has a
polymeric backbone and the groups A, D, and B are covalently bonded to
the polymeric backbone according to one or more structures selected from
the group consisting of AxDyBz, AxDy,
AxBz, DyBz, A, D, and B; wherein x and z are each
independently integers from 1 to 8 and y is 1 or 2.

22. A contrast dye according to claim 14, wherein the phosphorous
containing group capable of reacting with the surface of the lithographic
receiver is represented by Formula (I): ##STR00079## whereinX1,
X2, X3, and X4 are independently selected from oxygen or
sulfur;q represents 0 or 1;M1 is a proton or a counterion to
compensate for the negative charge of X4;M2 is a proton or a
counterion to compensate for the negative charge of X3 or represents
a substituted or unsubstituted, saturated or unsaturated aliphatic chain,
a substituted or unsubstituted aryl or hetero-aryl group.

23. A contrast dye according to claim 22, wherein the phosphorous
containing group capable of reacting with the surface of the lithographic
receiver represented by Formula (I) is selected from the group consisting
of --O--PO3H2, --O--PO3HR, --PO3H2 or
--PO3HR with R representing methyl or ethyl.

24. A contrast dye according to claim 14, wherein the aliphatic group
contains at least 5 fluorine atoms.

25. A contrast dye according to claim 14, wherein the aliphatic group
includes a fluorinated straight chain aliphatic group containing at least
6 carbon atoms.

26. A contrast dye according to claim 25, wherein the straight chain
aliphatic group is represented by --(CF2--CF2)nCF3
with n representing an integer between 3 and 20.

27. A contrast dye according to claim 14, wherein the aliphatic group is
represented by --(CH2--CH2)nCH3 with n representing
an integer between 3 and 20.

28. A contrast dye according to claim 14, wherein the chromophore group D
is selected from the group consisting of an azo dye with a molar
extinction coefficient larger than 10.sup.3/mol-1 cm-1, an
anthraquinone dye, a (poly)methine dye, an azomethine dye, a disazo dye,
a carbonium dye, a styryl dye, a stilbene dye, a phthalocyanine dye, a
coumarin dye, an aryl-carbonium dye, a nitro dye, a naphtholactam dye, a
dioxazine dye, a flavin dye, and a formazan dye.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is a 371 National Stage Application of
PCT/EP2006/069296, filed Dec. 5, 2006. This application claims the
benefit of U.S. Provisional Application No. 60/755,987, filed Jan. 4,
2006, which is incorporated by reference herein in its entirety. In
addition, this application claims the benefit of European Application No.
05112508.6, filed Dec. 20, 2005, which is also incorporated by reference
herein in its entirety.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to lithographic printing plates and
methods for their preparation by inkjet. More specifically, it relates to
a method for generating a visual contrast on the printing plate precursor
using contrast dyes which persist after gumming and other post treatments
of an imaged printing plate precursor.

[0004]2. Description of the Related Art

[0005]Over the last decade, the graphic arts workflow has changed
dramatically, evolving from a computer to film work flow to a computer to
plate workflow. Direct plate making is becoming the dominant technology
in the market, preferentially using thermal or photo-polymerization
technology. The majority of the commercial systems are processing
required systems, using an alkaline developer to process the plates after
imaging. In recent years, there is a clear tendency towards printing
plates requiring no processing, such as, for example, a developing step
to obtain the lithographic image.

[0006]Also over the last decade, the image quality of inkjet systems has
evolved to a level such that direct imaging of printing plate precursors
is an option that is competitive with the classical workflow. Direct
plate making by inkjet has been described in the patent literature.
Several conceptual approaches have been described. Directly
hydrophobizing lithographic printing plate precursors, using a
hydrophobic ink is a clearly preferred option.

[0007]Several types of hydrophobic inks have been described in the patent
literature. U.S. Pat. No. 6,742,886 (KPG) discloses a method of preparing
a printing plate by imagewise application onto a substrate of an
inkjettable composition consisting essentially of an oleophilic polymer
in an organic solvent. U.S. Pat. No. 5,511,477 (IDANIT TECH LTD)
discloses a method for the production of printing plates by inkjet
printing with a photopolymeric ink composition on a substrate and
subjecting the resulting printed substrate to UV radiation thereby curing
the ink composition.

[0008]Inkjet systems such as the ones of the foregoing patents make use of
organic solvent inks or UV-curing technology. However, aqueous based
inkjet inks, requiring only a drying step after jetting thereby greatly
reducing problems related to toxicology or to the complexity of the
design of plate setters, have become the preferred choice for designing
new inkjet plate setters.

[0009]An inkjet ink for direct plate making by inkjet has to meet several
requirements at the same time. The chemistry in the ink should allow:
[0010]dot spread control on the surface of the printing plate precursor
to guarantee the initial image quality, [0011]a high run length under
several press conditions, [0012]a good resistance against press
chemicals, and [0013]a good visual contrast on the plate to allow visual
inspection of the printing plate before mounting on the press and in
future re-use of the printing plate.

[0014]Several aqueous based inks have been disclosed for preparing
printing plates by inkjet.

[0015]EP 1157826 A (AGFA) discloses an aqueous inkjet fluid containing an
oleophilizing compound having in its chemical structure a 1,2-dihydroxy
aryl functional group, such as a catechol, a pyrogallol, and a salicylic
acid.

[0017]EP 1157828 A (AGFA) discloses an inkjet fluid containing an
oleophilizing compound containing a 1,3-dicarbonyl group in its chemical
formula.

[0018]EP 1211063 A (AGFA) discloses an inkjet fluid containing an
oleophilizing compound having in its chemical structure a boron
containing group capable of reacting with the surface of the lithographic
receiver.

[0019]EP 1219415 A (AGFA) discloses an inkjet fluid containing an
oleophilizing compound having in its chemical structure a functional
amidine group capable of reacting with the surface of a lithographic
receiver. Preferably, the amidine group is an imidazolidine group.

[0020]U.S. Pat. No. 6,532,871 (KPG) discloses a method of controlling the
resolution of an image formed on a substrate, including: (a) providing a
substrate; and (b) applying an image to the substrate by imagewise
directly applying upon the substrate a fluid composition including at
least one surfactant which is interfacially matched to the substrate, in
which the dot size of the fluid composition on the substrate in the
presence of the surfactant is less than the dot size of the fluid
composition on the substrate in the absence of the surfactant, wherein an
ink-absorbing layer is not applied to the substrate. In a preferred
embodiment fluorinated surfactants on an anodized aluminum support are
disclosed.

[0021]None of the above disclosed inkjet fluids containing a
hydrophobizing or oleophilizing compound generate the necessary plate
contrast for allowing visual inspection of the plate before mounting on
the press, or produces a printing plate still exhibiting good contrast in
the lithographic image after gumming or similar post-treatments. For good
contrast, the presence of a dye is required.

[0022]EP 1157825 A (AGFA) discloses an aqueous inkjet fluid containing an
oleophilizing compound having in its chemical structure a phosphorous
containing group capable of reacting with the surface of a lithographic
receiver. In the example, Acid Black (CI20470) is used as a dye.

[0023]EP 0882584 A (KODAK) discloses a method of preparing a printing
plate including producing an oleophilic image on the surface of a support
by inkjet printing the image on the surface using an aqueous solution or
aqueous colloidal dispersion of a salt of a hydrophobic organic acid. In
example 3, the dye Acid Blue 92 was used in the aqueous inkjet ink to
make the inkjet image more visible.

[0024]However, it has been found that Acid Black (CI20470), Acid Blue 92
and other dyes, such as crystal violet or Direct Blue 199 that are
frequently used in conventional lithographic plates, are not resistant
against gumming solutions used on printing plates prepared by inkjet. As
a result, the plate loses contrast upon gumming and visual inspection of
the plate is no longer possible.

SUMMARY OF THE INVENTION

[0025]Therefore, it would be desirable to have a method of preparing
lithographic printing plates using inkjet technology, which delivers
printing plates exhibiting good contrast of the lithographic image even
after gumming or other post-treatments and which avoids the use of
radiation curable materials or high concentrations of organic solvents.

[0026]The various preferred embodiments of the present invention provide
contrast dyes for preparing lithographic printing plates exhibiting good
contrast of the lithographic image even after gumming or other
post-treatments.

[0027]The various preferred embodiments of the present invention further
provide a lithographic printing plate exhibiting good contrast of the
lithographic image.

[0028]These and other advantages of preferred embodiments of the present
invention will become apparent from the description hereinafter.

[0029]It was discovered that lithographic images exhibiting good contrast
which persisted after gumming, were obtained by using an inkjet ink
including a special type of contrast dye having in its chemical structure
a phosphorous containing group capable of reacting with the surface of a
lithographic receiver, a chromophore group absorbing in the visual
spectrum and a hydrophobic aliphatic chain.

[0030]Moreover, it was discovered that it was possible to print with a
lithographic image derived from the inkjet ink including the special type
contrast dye without the need of adding an oleophilizing or ink-uptaking
compound.

[0031]Advantages of preferred embodiments of the present invention are
achieved with a contrast dye for preparing a lithographic printing plate
including at least one A, D and B group wherein A represents a
phosphorous containing group capable of reacting with the surface of a
lithographic receiver; D represents a chromophore group absorbing light
between 400 and 700 nm; and B represents an aliphatic group of at least 6
carbon atoms.

[0032]Advantages of preferred embodiments of the present invention are
also achieved with a lithographic printing plate including such a
contrast dye.

[0033]Other features, elements, steps, characteristics and advantages of
the present invention will become more apparent from the following
detailed description of preferred embodiments of the present invention
with reference to the attached drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Definitions

[0034]The term "lithographic printing plate" as used in the preferred
embodiments of the present invention means a plate having a lithographic
image on its surface.

[0035]The term "lithographic image" as used in the preferred embodiments
of the present invention means an image on a lithographic printing plate
consisting of printing areas and non-printing areas.

[0036]The term "printing areas" as used in the preferred embodiments of
the present invention means the areas of the image on a lithographic
printing plate that are ink-receptive.

[0037]The term "non-printing areas" as used in the preferred embodiments
of the present invention means the areas of the image on a lithographic
printing plate that are ink-repellent.

[0038]The term "lithographic printing plate precursor" as used in the
preferred embodiments of the present invention means any plate with a
surface capable of forming a lithographic image.

[0039]The term "dye", as used in the preferred embodiments of the present
invention, means a colorant having a solubility of 10 mg/L or more in the
medium in which it is applied and under the ambient conditions
pertaining.

[0040]The term "chromophore group", as used in the preferred embodiments
of the present invention, means a group with an absorption between 400 nm
and 700 nm.

[0041]The term "DP" is used in the preferred embodiments of the present
application as an abbreviation for degree of polymerization, i.e., the
number of structural units (monomers) in the average polymer molecule.

[0042]The term "alkyl" means all variants possible for each number of
carbon atoms in the alkyl group, i.e., for three carbon atoms: n-propyl
and isopropyl; for four carbon atoms: n-butyl, isobutyl and
tertiary-butyl; for five carbon atoms: n-pentyl, 1,1-dimethyl-propyl,
2,2-dimethylpropyl and 2-methyl-butyl etc.

[0043]The term "acyl group" means a --(C═O)-aryl group, a
--(C═O)-alkyl group, a --(C═O)-heteroaryl group and
--(C═O)-heterocyclic group.

[0046]The term "aromatic group" as used in the preferred embodiments of
the present invention means an assemblage of cyclic conjugated carbon
atoms, which are characterized by large resonance energies, e.g.,
benzene, naphthalene and anthracene.

[0047]The term "alicyclic hydrocarbon group" means an assemblage of cyclic
carbon atoms, which do not form an aromatic group, e.g., cyclohexane.

[0048]The term "substituted" as used in the preferred embodiments of the
present invention means that one or more of the carbon atoms and/or
hydrogen atoms of one or more of carbon atoms in an aliphatic group, an
aromatic group or an alicyclic hydrocarbon group, are replaced by another
atom, e.g., a halogen atom, an oxygen atom, a nitrogen atom, a silicon
atom, a sulphur atom, a phosphorous atom, selenium atom or a tellurium
atom. Such substituents include hydroxyl groups, ether groups, carboxylic
acid groups, ester groups, amide groups and amine groups.

[0049]The term "heteroaromatic group" means an aromatic group wherein at
least one of the cyclic conjugated carbon atoms is replaced by a
non-carbon atom such as a nitrogen atom, a sulphur atom, a phosphorous
atom, selenium atom and a tellurium atom.

[0050]The term "heterocyclic group" means an alicyclic hydrocarbon group
wherein at least one of the cyclic carbon atoms is replaced by an oxygen
atom, a nitrogen atom, a phosphorous atom, a silicon atom, a sulphur
atom, a selenium atom or a tellurium atom.

Inkjet Inks

[0051]An inkjet ink for preparing a lithographic printing plate contains
at least one contrast dye according to a preferred embodiment of the
present invention, but a mixture of two, three or more contrast dyes may
also be used.

[0052]The inkjet ink preferably contains water as the liquid carrier for
the contrast dye.

[0053]The inkjet ink may further contain at least one organic solvent. The
inkjet ink may have a liquid carrier of organic solvent(s) but the liquid
carrier is preferably aqueous for better control of the dotsize on a
printing plate.

[0054]The inkjet ink may further contain at least one oleophilizing
compound.

[0055]The inkjet ink may further contain at least one pH adjuster.

[0056]The viscosity of the inkjet ink is preferably lower than 100 mPas,
more preferably lower than 30 mPas, and most preferably lower than 15
mPas at a shear rate of 100 s-1 and a temperature between 20 and
70° C.

[0057]The contrast dye is preferably used in the inkjet ink for preparing
a lithographic printing plate in an amount of 0.1 to 20 wt %, more
preferably 0.2 to 10 wt % and most preferably 0.5 to 5 wt % based on the
weight of the inkjet ink.

Contrast Dyes

[0058]The contrast dye according to a preferred embodiment of the present
invention includes at least one A, D and B group wherein A represents a
phosphorous containing group capable of reacting with the surface of a
lithographic receiver; D represents a chromophore group absorbing light
between 400 and 700 nm; and B represents an aliphatic group of at least 6
carbon atoms.

[0059]The contrast dye may be a low molecular weight compound containing
preferably one or two A, D and B groups or may be a contrast dye having a
polymeric backbone including a plurality of A, D and B groups.

[0060]In the case of a low molecular weight compound, the contrast dye may
have the structure AxDyBz wherein x, y and z are each
independently chosen integers from 1 to 10 and the A and B groups are
covalently bonded to the chromophore group D. In a preferred embodiment,
x and z are each independently chosen integers from 1 to 8 and y is 1 or
2. In another preferred embodiment, X, Y and Z all represent the integer
1.

A Groups

[0061]In a preferred embodiment, the phosphorous containing group capable
of reacting with the surface of a lithographic receiver is represented by
Formula (I):

##STR00001##

wherein X1, X2, X3 and X4 are independently selected
from oxygen or sulfur;q represents 0 or 1;M1 is a proton or a
counterion to compensate for the negative charge of X4;M2 is a
proton or a counterion to compensate for the negative charge of X3
or represents a substituted or unsubstituted, saturated or unsaturated
aliphatic chain, a substituted or unsubstituted aryl or hetero-aryl
group.

[0062]Preferably, the phosphorous containing group capable of reacting
with the surface of a lithographic receiver represented by Formula (I) is
selected from the group consisting of --O--PO3H2,
--O--PO3HR, --PO3H2 or --PO3HR with R representing
methyl or ethyl.

B Groups

[0063]The group B functions as an oleophilizing group. The group B
represents an aliphatic group of at least 6 carbon atoms, more preferably
at least 8 carbon atoms and most preferably at least 10 carbon atoms. In
a preferred embodiment, the carbon atoms form a straight chain aliphatic
group of at least 6 carbon atoms, more preferably at least 8 carbon atoms
and most preferably at least 10 carbon atoms.

[0064]The aliphatic group preferably contains one or more fluorine atoms,
preferably the aliphatic group is a fluorinated straight chain aliphatic
group containing at least 6 carbon atoms, more preferably at least 8
carbon atoms and most preferably at least 10 carbon atoms. In a preferred
embodiment, the aliphatic group B contains at least 5 fluorine atoms,
more preferably at least 9 fluorine atoms and most preferably at least 13
fluorine atoms.

[0065]In a preferred embodiment, the straight chain aliphatic group B may
be represented by --(CH2--CH2)nCH3 wherein n is an
integer between 3 and 20, more preferably between 4 and 16, and most
preferably between 5 and 14.

[0066]In another preferred embodiment, the straight chain aliphatic group
B may be represented by --(CF2--CF2)nCF3 wherein n is
an integer between 3 and 20, more preferably between 3 and 10.

D Groups

[0067]Any dye absorbing light between 400 and 700 nm may be used for the
chromophore group D in the contrast dye. The dye may have a wavelength of
maximum absorption λmax located outside the wavelength region
of 400 and 700 nm, for example at 320 nm or at 830 nm, as long as a
sufficient portion of light is absorbed between 400 and 700 nm, such that
it allows the human eye to differentiate printing areas from non-printing
areas on the lithographic printing plate.

[0068]Suitable dyes may be selected from the group consisting of an azo
dye with a molar extinction coefficient larger than 103/mol-1
cm-1, an anthraquinone dye, a (poly)methine dye, an azomethine dye,
a disazo dye, a carbonium dye, a styryl dye, a stilbene dye, a
phthalocyanine dye, a coumarin dye, an aryl-carbonium dye, a nitro dye, a
naphtholactam dye, a dioxazine dye, a flavin dye and a formazan dye.

[0069]Suitable examples of low molecular weight contrast dyes according to
a preferred embodiment of the present invention are given in Table 1,
without being limited thereto.

[0070]In another preferred embodiment, a contrast dye having a polymeric
backbone is used in the inkjet ink for preparing a lithographic printing
plate wherein the A, D and B groups are either directly or indirectly
covalently bonded to the polymeric backbone according to one or more
structures selected from the group consisting of AxDyBz,
AxDy, AxBz, DyBz, A, D and B; and wherein x
and z are each independently chosen integers from 1 to 8 and y is 1 or 2.

[0071]Examples of contrast dyes having a polymeric backbone are given in
Table 2, without being limited thereto.

[0072]A preferred embodiment for the contrast dye having a polymeric
backbone is exemplified by contrast dye CPOL-5: the chromophore group D
is covalently bonded to the polymeric backbone and one or more A and B
groups are covalently bonded to the chromophore group D.

[0073]Another preferred embodiment for the contrast dye having a polymeric
backbone, exemplified by contrast dyes CPOL-1 and CPOL-2, is: the
chromophore group D is covalently bonded to the polymeric backbone and
one or more A groups are covalently bonded to the chromophore group D,
while the B groups are directly covalently bonded to the polymeric
backbone.

[0074]Another preferred embodiment for the contrast dye having a polymeric
backbone, exemplified by contrast dye CPOL-4, is: the chromophore group D
is covalently bonded to the polymeric backbone and one or more B groups
are covalently bonded to the chromophore group D, while the A groups are
covalently bonded to the polymeric backbone.

[0075]Another preferred embodiment for the contrast dye having a polymeric
backbone, exemplified by contrast dye CPOL-3, is: the chromophore group
D, the group A and group B are all separately covalently bonded to the
polymeric backbone.

[0076]Suitable contrast dyes having a polymeric backbone may combine
several different structures selected from the group consisting of
AxDyBz, AxDy, AxBz, DyBz, A,
D and B, wherein x and z are each independently chosen integers from 1 to
8 and y is 1 or 2. For example, the contrast dye CPOL-6 has a polymeric
backbone substituted with x D groups, y A1B1 groups, and p A
groups.

[0077]A contrast dye having a polymeric backbone is preferably used in the
inkjet ink for preparing a lithographic printing plate according to a
preferred embodiment of the present invention in an amount of 1 to 10 wt
%, preferably 2 to 6 wt % based on the weight of the inkjet ink.

Polymeric Backbones

[0078]The polymeric backbone of the contrast dye according to a preferred
embodiment of the present invention contains monomers with the group
AxDyBz, AxDy, AxBz, DyBz, A,
D and/or B attached to it and optionally other monomers. The groups
AxDyBz, AxDy, AxBz, DyBz, A,
D and/or B may be linked to the monomer by any linking group. Preferably,
the linking group contains at least one carbon atom, one nitrogen atom,
one oxygen atom, one phosphorous atom, one silicon atom, one sulphur
atom, one selenium atom or one tellurium atom.

[0079]The linking group may be the result of modification of a monomer
with the group AxDyBz, AxDy, AxBz,
DyBz, A, D or B having a reactive group. Suitable reactive
groups include thiol groups, primary or secondary amino groups,
carboxylic acid groups or salts thereof, hydroxyl groups, isocyanate
groups and epoxy groups. Typical covalent bonds formed by reaction
include an amide, an ester, a urethane, an ether and a thioether.

[0082]Comb/branched polymers have side branches of linked monomer
molecules protruding from various central branch points along the main
polymer chain (at least 3 branch points).

[0083]Star polymers are branched polymers in which three or more either
similar or different linear homopolymers or copolymers are linked
together to a single core.

[0084]Dendritic polymers include the classes of dendrimers and
hyperbranched polymers; in dendrimers with well-defined mono-disperse
structures all branch points are used (multi-step synthesis), while
hyperbranched polymers means polymers having a plurality of branch points
and multifunctional branches that lead to further branching with polymer
growth (one-step polymerization process).

[0085]A general review on the architecture of polymers is given by ODIAN,
George, Principles Of Polymerization, 4th Edition, Wiley-Interscience,
2004, pp. 1-19.

[0086]Monomers lacking the group AxDyBz, AxDy,
AxBz, DyBz, A, D or B may be included in the
polymeric backbone for various purposes. Sometimes it is necessary to
include a number of monomers to improve the solubility in the inkjet ink
or to lower its viscosity. In other cases, specific monomers are included
to further enhance the chemical resistance of the printing plate during
the printing process when gum solutions and other solutions containing
aggressive organic solvents are used.

[0087]The polymeric backbone consists preferably of no more than 2, 3 or 4
monomer species.

[0088]The monomers lacking the group AxDyBz,
AxDy, AxBz, DyBz, A, D or B used to prepare
the contrast dye can be any monomer and/or oligomer found in the Polymer
Handbook, Vol. 1+2, 4th Edition, edited by J. BRANDRUP et al.,
Wiley-Interscience, 1999.

[0089]Suitable examples of monomers include: acrylic acid, methacrylic
acid, maleic acid, acryloyloxybenzoic acid and methacryloyloxybenzoic
acid (or their salts), maleic anhydride; alkyl(meth)acrylates (linear,
branched and cycloalkyl) such as methyl(meth)acrylate,
n-butyl(meth)acrylate, tert-butyl(meth)acrylate, cyclohexyl(meth)acrylate
and 2-ethylhexyl(meth)acrylate; aryl(meth)acrylates such as
benzyl(meth)acrylate and phenyl(meth)acrylate;
hydroxyalkyl(meth)acrylates such as hydroxyethyl(meth)acrylate and
hydroxypropyl(meth)acrylate; (meth)acrylates with other types of
functionalities (e.g., oxirane, amino, fluoro, polyethylene oxide,
phosphate-substituted) such as glycidyl (meth)acrylate,
dimethylaminoethyl(meth)acrylate, trifluoroethyl acrylate,
methoxypolyethyleneglycol (meth)acrylate and
tripropyleneglycol(meth)acrylate phosphate; allyl derivatives such as
allyl glycidyl ether; styrenics such as styrene, 4-methylstyrene,
4-hydroxystyrene, and 4-acetoxystyrene; (meth)acrylonitrile;
(meth)acrylamides (including N-mono and N,N-disubstituted) such as
N-benzyl (meth)acrylamide; maleimides such as N-phenyl maleimide,
N-benzyl maleimide and N-ethyl maleimide; vinyl derivatives such as
vinylcaprolactam, vinylpyrrolidone, vinylimidazole, vinylnaphthalene and
vinyl halides; vinylethers such as vinylmethyl ether; and vinylesters of
carboxylic acids such as vinylacetate and vinylbutyrate.

[0090]Specific monomers to further enhance the chemical resistance of the
printing plate during the printing process include a monomer represented
by the general formula:

##STR00053##

in which R is --H or --CH3; X is a bivalent linking group; Y is a
substituted or unsubstituted bivalent aromatic group; and Z is --OH,
--COOH, or --SO2NH2. R is preferably CH3. Preferably, X is
a substituted or unsubstituted alkylene group, substituted or
unsubstituted phenylene [C6H4] group, or substituted or
unsubstituted naphthalene [C10H6] group; such as
--(CH2)n--, in which n is 2 to 8; 1,2-, 1,3-, and
1,4-phenylene; and 1,4-, 2, 7-, and 1,8-naphthalene. More preferably, X
is unsubstituted and even more preferably n is 2 or 3; most preferably X
is --(CH2CH2)--. Preferably, Y is a substituted or
unsubstituted phenylene group or substituted or unsubstituted naphthalene
group; such as 1,2-, 1,3-, and 1,4-phenylene; and 1,4-, 2,7-, and
1,8-naphthalene. More preferably, Y is unsubstituted, most preferably
unsubstituted 1,4-phenylene. Z is --OH, --COOH, or --SO2 NH2,
preferably --OH.

[0091]A preferred monomer is:

##STR00054##

[0092]in which Z is --OH, --COOH, or --SO2NH2, preferably --OH.

[0093]Other suitable monomers to further enhance the chemical resistance
of the printing plate during the printing process include a monomer
represented by the general formula:

##STR00055##

in which R1 is --H or --CH3; R2 is --NH--R3 or --NCH3--R3; R3 is
a substituted or unsubstituted, saturated or unsaturated alkyl, a
substituted or unsubstituted aryl or hetero-aryl group. Preferably, R1 is
--CH3. More preferably, R2 is selected from the group consisting of
--NH2,

##STR00056##

[0094]Other suitable monomers to further enhance the chemical resistance
of the printing plate during the printing process include

##STR00057##

in which R is --H or --CH3. Preferably, R is --CH3.

[0095]The contrast dye having a polymeric backbone according to a
preferred embodiment of the present invention preferably has a polymeric
backbone with a polymerization degree DP between 5 and 1,000, more
preferably between 10 and 500 and most preferably between 10 and 100.

[0096]The contrast dye having a polymeric backbone according to a
preferred embodiment of the present invention preferably has a number
average molecular weight Mn between 500 and 30,000, more preferably
between 1,500 and 10,000.

Oleophilizing Compounds

[0097]An oleophilizing compound or hydrophobizing compound may be added to
the inkjet ink to form in combination with the contrast dye the printing
areas of the lithographic image. The oleophilizing compound on its own is
not capable of delivering a good contrast between the printing and the
non-printing areas of the lithographic image.

[0098]The hydrophobizing compound is preferably selected from the group
consisting of a phosphate or salt thereof, a phosphonate or salt thereof,
a boronic acid derivative, a 1,3-dicarbonyl compound, an imidazoline
derivative and a catechol or pyrogallol derivative. Phosphates and
phosphonates are particularly preferred.

[0099]Suitable hydrophobizing compounds may be selected from those
disclosed in EP 1157825 A (AGFA), EP 1157826 A (AGFA), EP A (AGFA), EP
1157828 A (AGFA), EP 1211063 A (AGFA), EP A (AGFA), U.S. Pat. No.
6,532,871 (KPG) and EP 0882584 A (KODAK).

[0100]In a preferred embodiment, the inkjet ink contains a
fluorosurfactant as an oleophilizing compound.

[0101]Illustrative examples of fluorosurfactants useful as oleophilizing
compound are FLUORAD® surfactants and ZONYL® surfactants. FLUORAD
surfactants are commercially available from 3M Company and have a narrow
distribution of the hydrophobic chain length. ZONYL® surfactants are
commercially available from E. I. du Pont de Nemours & Co. and have a
distribution of perfluoroalkyl chain length. Suitable ZONYL®
surfactants include ZONYL® FSA, ZONYL® FSP, ZONYL® FSE and
ZONYL® FSN.

[0102]Particularly preferred fluorosurfactants are selected from the group
consisting of
(F(CF2CF2)3-8CH2CH2O)1,2P(O)(ONH4).sub-
.2,1.

Organic Solvents

[0103]The inkjet ink may further contain at least one organic solvent, for
example, to dissolve the contrast dye better. The organic solvent is
preferably added to the inkjet ink in an amount of 1 to 40 wt %, more
preferably 2 to 20 wt %, and most preferably 5 to 10 wt % each based on
the total weight of the inkjet ink.

[0105]An organic solvent can also be present in the inkjet ink as a
humectant to prevent the clogging of the nozzle, due to its ability to
slow down the evaporation rate of ink.

[0106]Suitable humectants include triacetin, N-methyl-2-pyrrolidone,
glycerol, urea, thiourea, ethylene urea, alkyl urea, alkyl thiourea,
dialkyl urea and dialkyl thiourea, diols, including ethanediols,
propanediols, propanetriols, butanediols, pentanediols, and hexanediols;
glycols, including propylene glycol, polypropylene glycol, ethylene
glycol, polyethylene glycol, diethylene glycol, tetraethylene glycol, and
mixtures and derivatives thereof. Preferred humectants are ethylene
glycol, propylene glycol, diethylene glycol, dipropylene glycol,
triethylene glycol mono methyl ether, triethylene glycol mono butylether,
glycerol and 1,2-hexanediol. The humectant is preferably added to the
inkjet ink in an amount of 0.1 to 40 wt %, more preferably 2 to 35 wt %,
and most preferably approximately 10 to 30 wt % each based on the total
weight of the inkjet ink. The total amount of organic solvent and
humectant in the inkjet ink is preferably in the range of 5 to 40 wt %,
more preferably 15 to 30 wt % each based on the total weight of the
inkjet ink.

pH Control Agents

[0107]A pH control agent may also be present in the inkjet ink. The inkjet
ink preferably has a pH from 3 to 8, more preferably from 4 to 6. The pH
of the inkjet ink is usually adjusted with an acid or a base such as a
mineral acid, an organic acid, an organic base or an inorganic salt.

[0111]The mineral acid, organic acid or inorganic salt may be used singly
or in combination with one or more thereof.

Lithographic Printing Plates

[0112]The lithographic printing plate contains a contrast dye including A,
D and B groups wherein A represents a phosphorous containing group
capable of reacting with the surface of a lithographic receiver; D
represents a chromophore group absorbing light between 400 and 700 nm;
and B represents an aliphatic group of at least 6 carbon atoms. The
lithographic printing plate can be obtained by a method for direct plate
making by jetting on a printing plate precursor an inkjet ink including a
contrast dye according to a preferred embodiment of the present
invention.

[0113]The lithographic printing plate may be a sheet-like material such as
a plate or it may be a cylindrical element such as a sleeve which can be
slid around a print cylinder of a printing press.

[0114]In a preferred embodiment, a gum solution is jetted on at least the
lithographic non-image, but preferably the gum solution is jetted only on
the non-printing areas of the lithographic printing plate.

Lithographic Supports

[0115]A particularly preferred lithographic support is an
electrochemically grained and anodized aluminum support. Graining and
anodizing of aluminum supports is well known. The acid used for graining
can be, e.g., nitric acid or sulfuric acid. The acid used for graining
preferably includes hydrogen chloride. Also mixtures of, e.g., hydrogen
chloride and acetic acid can be used. The relationship between
electrochemical graining and anodizing parameters such as electrode
voltage, nature and concentration of the acid electrolyte or power
consumption on the one hand and the obtained lithographic quality in
terms of Ra and anodic weight (g/m2 of Al2O3 formed on the
aluminum surface) on the other hand is well known. More details about the
relationship between various production parameters and Ra or anodic
weight can be found in, e.g., the article "Management of Change in the
Aluminium Printing Industry" by F. R. Mayers, published in the ATB
Metallurgie Journal, volume 42 no. 1-2, (2002), page 69.

[0116]With regard to the anodizing treatment, methods that have been
conventionally used in this field can be used. Specifically, when direct
or alternative current is fed to the aluminum plates in aqueous solution
or non aqueous solution, alone or in combination, of sulfuric acid,
phosphoric acid, chromic acid, oxalic acid, sulfamic acid,
benzenesulfonic acid and the like, an anodized layer can be formed on the
surface of the aluminum plate. Since conditions for anodizing treatment
change variously depending on the electrolyte being used, those are not
decided unconditionally, but it is generally appropriate that the
concentration of electrolyte is 1 to 80 wt %, temperature of solution is
8 to 70° C., preferably 25 to 55° C., current density is
0.5 to 70 A/dm2, preferably 15 to 60 A/dm2, voltage is 1 to 200
V, and time for electrolysis is 1 to 100 seconds, preferably 5 to 60
seconds.

[0117]The anodized aluminum support may be subject to a so-called
post-anodic treatment to improve the hydrophilic properties of its
surface. For example, the aluminum support may be silicated by treating
its surface with a sodium silicate solution at elevated temperature,
e.g., 95° C. Alternatively, a phosphate treatment may be applied
which involves treating the aluminum oxide surface with a phosphate
solution that may further contain an inorganic fluoride. Further, the
aluminum oxide surface may be rinsed with a citric acid or citrate
solution. This treatment may be carried out at room temperature or may be
carried out at a slightly elevated temperature of about 30 to 50°
C. A further interesting treatment involves rinsing the aluminum oxide
surface with a bicarbonate solution. Still further, the aluminum oxide
surface may be treated with polyvinylphosphonic acid,
polyvinylmethylphosphonic acid, phosphoric acid esters of polyvinyl
alcohol, polyvinylsulfonic acid, polyvinylbenzenesulfonic acid, sulfuric
acid esters of polyvinyl alcohol, and acetals of polyvinyl alcohols
formed by reaction with a sulfonated aliphatic aldehyde.

[0118]Another useful post-anodic treatment may be carried out with a
solution of polyacrylic acid or a polymer including at least 30 mol % of
acrylic acid monomeric units, e.g., GLASCOL E15, a polyacrylic acid,
commercially available from ALLIED COLLOIDS.

[0119]The grained and anodized aluminum support may be a sheet-like
material such as a plate or it may be a cylindrical element such as a
sleeve which can be slid around a print cylinder of a printing press.

[0120]The support can also be a flexible support, which may be provided
with a hydrophilic layer, hereinafter called `base layer`. The flexible
support is, e.g., paper, plastic film or aluminum. Preferred examples of
plastic film are polyethylene terephthalate film, polyethylene
naphthalate film, cellulose acetate film, polystyrene film, polycarbonate
film, etc. The plastic film support may be opaque or transparent.

[0121]The base layer is preferably a cross-linked hydrophilic layer
obtained from a hydrophilic binder cross-linked with a hardening agent
such as formaldehyde, glyoxal, polyisocyanate or a hydrolyzed
tetra-alkylorthosilicate. The latter is particularly preferred. The
thickness of the hydrophilic base layer may vary in the range of 0.2 to
25 μm and is preferably 1 to 10 μm. More details of preferred
embodiments of the base layer can be found in, e.g., EP 1025992 A (AGFA).

Inkjet Printing Process

[0122]In ink jet printing, tiny drops of ink fluid are projected directly
onto an ink receptor surface without physical contact between the
printing device and the receptor. The printing device stores the printing
data electronically and controls a mechanism for ejecting the drops
image-wise. Printing may be accomplished by moving the print head across
the lithographic receiver or vice versa. The inkjet printing may also be
a "single pass printing process". This is a printing mode, which can be
performed by using page wide inkjet printing heads or multiple staggered
inkjet printing heads that cover the entire width of the ink-receiver
surface. In a single pass printing process, the inkjet printing heads
usually remain stationary and the ink-receiver surface is transported
under the inkjet printing heads. An example of such a single pass inkjet
printer is "The Dot Factory" manufactured by AGFA DOTRIX.

[0123]The jetting of the ink droplets can be performed in several
different ways. In a first type of process, a continuous droplet stream
is created by applying a pressure wave pattern. This process is known as
continuous ink jet printing. In a first preferred embodiment, the droplet
stream is divided into droplets that are electrostatically charged,
deflected and recollected, and into droplets that remain uncharged,
continue their way undeflected, and form the image. Alternatively, the
charged deflected stream forms the image and the uncharged undeflected
jet is recollected. In this variant of continuous ink jet printing,
several jets are deflected to a different degree and thus record the
image (multideflection system).

[0124]According to a second process, the ink droplets can be created "on
demand" ("DOD" or "drop on demand" method) whereby the printing device
ejects the droplets only when they are used in imaging a receiver thereby
avoiding the complexity of drop charging, deflection hardware, and ink
recollection. In drop-on-demand, the ink droplet can be formed by a
pressure wave created by a mechanical motion of a piezoelectric
transducer (so-called "piezo method"), or by discrete thermal pushes
(so-called "bubble jet" method, or "thermal jet" method).

[0125]In a preferred embodiment of the method for direct plate making, the
inkjet printer is mounted on the printing press. For colored printing
matter, the printing press usually includes four print cylinders. A plate
is mounted on each print cylinder for each of the four printing inks
(CMYK); in this case each print cylinder may have its own inkjet printer.

[0126]In another preferred embodiment, the hue of the jetted printing
areas on the printing plate precursor corresponds with the hue of the
printing ink to be used with the printing plate. For example, for a CMYK
printing process, the printing plate having the lithographic image for
printing with the cyan printing ink has a cyan hue, the printing plate
having the lithographic image for printing with the magenta printing ink
has a magenta hue, the printing plate having the lithographic image for
printing with the yellow printing ink has a yellow hue, and the printing
plate having the lithographic image for printing with the black printing
ink has a dark hue. The advantage of this method is that errors in
mounting a printing plate on the wrong printing press are eliminated and
that no extra markings on the printing plate are required for identifying
the color selection with which the printing plate corresponds.

[0127]In another preferred embodiment of the method for direct plate
making, a gum solution is jetted on the lithographic non-image, i.e., the
non-printing areas of the lithographic image. In this case, the inkjet
printer has at least one print head ejecting small droplets of gum
solution in a controlled manner through nozzles onto the surface of a
lithographic printing plate, which is moving relative to the printing
head(s). The jetted gum solution forms a hydrophilic protective layer on
the non-printing areas and optionally the printing areas of the
lithographic printing plate. Preferably, the gum solution for the
non-printing areas is jetted in the same printing process with the inkjet
ink used to form the printing areas of a lithographic image on a
lithographic printing plate. According to another preferred embodiment,
the gum solution for the non-printing areas and the inkjet ink used to
form the printing areas of lithographic image on the lithographic
printing plate are jetted by the same inkjet print head.

Gum Solutions

[0128]A gum solution suitable for use in a method for direct plate making
is an aqueous liquid, which includes one or more surface protective
compounds that are capable of protecting the lithographic image of a
printing plate against contamination or damaging. Suitable examples of
such compounds are film-forming hydrophilic polymers and surfactants. The
hydrophilic protective layer that remains on the plate after treatment
with the gum solution preferably includes between 0.1 and 20 g/m2 of
the surface protective compound, particularly preferably between 0.15 and
0.3 g/m2 of the surface protective compound.

[0129]For jetting with an inkjet printer, the viscosity of the gum
solution is preferably lower than 100 mPas, more preferably lower than 50
mPas, and most preferably lower than 30 mPas at a shear rate of 100
s-1 and a temperature between 20 and 110° C.

[0130]A special type of gum solution is a baking gum solution having a
similar composition as a standard gum solution, but with the additional
preference towards compounds that do not evaporate at the usual bake
temperatures.

[0132]After applying the baking gum solution, the plate can be dried
before baking or is dried during the baking process itself. The baking
process can proceed at a temperature between 100° C. and
230° C. for a period of 5 to 40 minutes. For example, a
lithographic printing plate jetted upon with a baking gum can be baked at
a temperature of 230° C. for 5 minutes, at a temperature of
150° C. for 10 minutes or at a temperature of 120° C. for
30 minutes. Baking can be done in conventional hot air ovens or by
irradiation with lamps emitting in the infrared or ultraviolet spectrum.

Hydrophilic Polymers

[0133]The hydrophilic polymers suitable as surface protective compounds in
the gum solution are polymers including ionic or ionizable groups or
containing polyethyleneoxide groups.

[0134]Examples of ionic or ionizable groups are acid groups or salts
thereof such as carboxylic acid group, sulphonic acid, phosphoric acid or
phosphonic acid. The acid groups in the polymer may be neutralized with
an organic amine (e.g., ammonia, triethylamine, tributylamine,
dimethylethanolamine, diisopropanolamine, morpholine, diethanolamine or
triethanolamine) or an alkali metal (e.g., lithium, sodium or potassium).
The polymer may be composed of a monomer including an anionic group. The
polymer may also be composed of two or more different types of monomers
including anionic and/or non-ionic groups. Specific examples of monomers
including anionic groups are (meth)acrylic acid, crotonic acid,
(meth)acrylic acid, propyl(meth)acrylic acid, isopropyl(meth)acrylic
acid, itaconic acid, fumaric acid, sulfoethyl(meth)acrylate,
butyl(meth)acrylamidesulfonic acid and phosphoethyl(meth)acrylate. In
general, the number average molecular weight of the polymer is preferably
in the range of about 1,000 to 3,000,000 g/mol.

[0135]Preferred polymers for use as the protective compound in the gum
solution are gum arabic, pullulan, cellulose derivatives such as
carboxymethylcellulose, carboxyethylcellulose or methylcellulose,
(cyclo)dextrin, poly(vinyl alcohol), poly(vinyl pyrrolidone),
polysaccharide, homo- and copolymers of acrylic acid, methacrylic acid or
acrylamide, a copolymer of vinyl methyl ether and maleic anhydride, a
copolymer of vinyl acetate and maleic anhydride or a copolymer of styrene
and maleic anhydride. Highly preferred polymers are homo- or copolymers
of monomers containing carboxylic, sulfonic or phosphonic groups or the
salts thereof, e.g., (meth)acrylic acid, styrene sulfonic acid, vinyl
sulfonic acid, vinyl phosphonic acid or acrylamidopropane sulfonic acid.

Surfactants

[0136]The gum solution may include one or more surfactants to improve the
surface properties of the jetted hydrophilic protective layer. The
surfactant may be an anionic or a non-ionic surfactant.

[0140]Two or more of the above surfactants may be used in combination. For
example, a combination of two or more different anionic surfactants or a
combination of an anionic surfactant and a non-ionic surfactant may be
preferred. The amount of such a surfactant is not specifically limited
but is preferably from 0.01 to 20 wt %.

[0141]The surface tension of the gum solution is preferably from 20 to 50
mN/m, more preferably from 25 to 35 mN/m.

pH Control Agents

[0142]A pH control agent may also be present in the gum solution. The pH
of the gum solution is usually adjusted with an acid or a base such as a
mineral acid, an organic acid, an organic base or an inorganic salt.

[0148]The wetting agent may be used singly or in combination with one or
more thereof.

[0149]In general, the foregoing wetting agent is preferably used in an
amount of from 0.1 to 25 wt %.

Chelate Compounds

[0150]A chelate compound may also be present in the gum solution. Calcium
ion and other impurities contained in the gum solution can have adverse
effects on printing and thus cause the contamination of printed matter.
Adding a chelate compound to the gum solution can eliminate this problem.

[0154]The preferred amount of such an antiseptic to be added is such that
it can exert a stable effect on bacteria, fungi, yeast or the like.
Though depending on the kind of bacteria, fungi and yeast, it is
preferably from 0.01 to 4 wt % relative to the gum solution.

[0155]Further, preferably, two or more antiseptics may be used in
combination to exert an aseptic effect on various fungi and bacteria.

Anti-Foaming Agents

[0156]An anti-foaming agent may also be present in the gum solution. The
anti-foaming agent is preferably a silicone anti-foaming agent. Among
these anti-foaming agents, either an emulsion dispersion type or a
solubilized type anti-foaming agent may be used.

[0157]The proper amount of such an anti-foaming agent to be added is from
0.001 to 1.0 wt % relative to the gum solution.

Ink Receptivity Agents

[0158]When gum solution is also jetted on the printing areas of the
lithographic printing plate, an ink receptivity agent may also be present
in the gum solution to ensure a rapid adhesion of printing ink. If the
gum solution is solely jetted on the non-printing areas, then preferably
no ink receptivity agent is present in the gum solution.

[0161]The ink receptivity agent may be used singly or in combination with
one or more thereof. The ink receptivity agent is preferably used in an
amount of from 0.01 to 10 wt %, more preferably from 0.05 to 5 wt %. The
foregoing ink receptivity agent may be present as an oil-in-water.

[0162]The preferred embodiments of the present invention will now be
illustrated by the following examples without however being limited
thereto.

EXAMPLES

Materials

[0163]All materials used in the following examples were readily available
from Aldrich Chemical Co. (Belgium) unless otherwise specified. The
"water" used in the examples was demineralized water. The following
materials were used:

Zonyl® FSE from DuPont.DYE-1 is methylorange from MERCK.DYE-5 is C.I.
Direct Blue 199 for which Duasyn® Direct

Turquoise Blue

[0164]FRL-SF from CLARIANT Benelux NV was used.(4-aminobenzyl)-phosphonic
acid diethyl ester from ALDRICH.Propyleneglycol from CALDIC Belgium
NV.Diethyleneglycol from BASF Belgium NV.2-pyrrolidone from
BASF.Ethyleneglycol from UCB.TEGMBE is an abbreviation for
Triethyleneglycolmonobutylether from VEL.SMA1000P is a styrene maleic
anhydride alternating copolymer supplied by CRAY VALLEY.SAA is a grained
and anodized aluminum substrate. Graining was carried out in a 2 cell
grainer using HCl (9.5 and 9.7 g/L respectively)/CH3COOH (17.6 and
18.5 g/L respectively) as an acid mixture, at a temperature of
26.5° and 25.3° C. and voltages of 21 and 22V. Anodization
was carried out in 2 cells containing sulfuric acid (129 g/L and 119 g/L
respectively) at 45° C. and 46.1° C. and voltages of 25.9V
and 25V resulting in an anodic weight of 6.6 g/m2.MAA differs from
the method for preparing SAA substrate in that the anodization was
carried out in a mixture of H3PO4 and H2SO4 (resp.
332 g/L and 52.9 g/L). The temperature of the anodization liquid was
44° C. and the resulting anodic weight was 2.43 g/m2.

Measurement Methods

1. Visual Contrast

[0165]A visual evaluation of the contrast in the lithographic image was
performed by depositing a series of 2 or 3 dots of inkjet ink onto a
lithographic printing plate precursor at room temperature using a 2 μL
pipette. SAA and MAA were used as lithographic plate precursors. After
drying the dots using a heat treatment of 15 minutes at 120° C.,
the contrast was evaluated in accordance with a criterion described
below.

Criterion:

[0166]OK=a clear visual image of dots was observed.

[0167]Not OK=a poor image of dots was observed.

[0168]None=no image of dots could be observed.

2. Gum Contrast

[0169]The same lithographic plates having a series of dots used to
evaluate the visual contrast were subsequently used to evaluate the
contrast again after a gumming treatment.

[0170]A gum solution was prepared by diluting the gum RC 795 from AGFA
with water to 50% of the original concentration. The gum solution was
applied to the printing plate using a custom built clean-out unit. The
printing plate was transported by a pair of driving rollers at a speed of
one meter per minute. Gum was sprayed through a number of openings in
three tubes. One of those tubes sprayed directly onto the printing plate,
two other sprayed against a cylindrical brush situated further in the
transportation path. This brush made contact with the printing plate.
After the gum was applied, the printing plate was transported by a roller
pair into a drying zone where the applied gum solution was dried with air
of 47° C. The contrast was evaluated in accordance with a
criterion described below.

Criterion:

[0171]OK=the clear visual image of dots was still observed.

[0172]Not OK=a poor image of dots was observed.

[0173]None=no image of dots could be observed.

3. Printing Test

[0174]The same lithographic plates having a series of dots used to
evaluate the visual contrast and the gum contrast were subsequently used
to evaluate the printing quality.

[0175]The printing quality was investigated by mounting the printing plate
on a Heidelberg sheet fed GTO46 offset press using a mixture of 3%
FS101® and 10% isopropanol as a fountain solution. Skinnex X800 black
ink was used for printing on Rey Today Office Paper 80 g/m2
delivered by GPG Papier NV. The optical density of the unprinted paper
was 0.09.

[0176]A good printing quality requires a thorough clean-out in the
non-printing areas and a rapid ink-uptake in the printing areas, i.e.,
the series of dots. A thorough clean-out means that, after a low number
of prints, the optical density of a non-printing area on the paper was
approximately equal to that of the unprinted paper. The ink-uptake was
evaluated by visual inspection of the printing area on the paper after a
number of prints. A rapid ink-uptake means that a high optical print
density was obtained after a low number of prints. The ink-uptake was
evaluated in accordance with a criterion described below.

Criterion:

[0177]OK=rapid ink-uptake, printed image of high optical density after 10
revolutions of the offset press.

[0178]Not OK=no printed image or a poor printed mage was observed after
100 revolutions of the offset press.

[0180]The starting black blue dye was prepared according to Example A of
EP 0771860 A (SEIKO EPSON).

[0181]5 g of the starting black blue dye (8 mmol) was dissolved in 30 mL
dimethyl acetamide. Then 1.4 mL (9.7 mmol) triethylamine was added. 2.8 g
(11.3 mmol) of myristoyl chloride was added dropwise to the reaction
mixture. The reaction was allowed to continue for 1 hour at room
temperature. Contrast dye CD-1 partially precipitated from the medium,
was isolated by filtration and washed with a small amount of dimethyl
acetamide and ethylacetate. The filtrate was diluted with 300 mL ethyl
acetate and a second fraction of contrast dye 1 precipitated. The second
fraction was isolated by filtration and washed several times with 50 mL
ethyl acetate. The pooled fractions were dried under vacuum.

[0182]Contrast dye CD-2 was prepared according to the same procedure,
using stearoyl chloride in stead of myristoyl chloride.

[0185]Acylation of N-(2-aminoethyl)-N-ethyl-aniline: 20 g (0.12 mol) of
N-(2-aminoethyl)-N-ethyl-aniline was dissolved in 100 mL of acetonitrile.
16.9 mL (0.12 mol) of triethylamine was added to this solution. A
solution of 32 g (0.076 mol) of pentadecafluorooctanoyl chloride in 65 mL
acetonitrile is added dropwise over 30 minutes. The reaction was allowed
to continue for an additional 2 hours at room temperature. The
precipitated triethylamine chlorohydrate was removed by filtration and
the filtrate was diluted with 400 mL of a 1.2 N hydrochloric acid
solution. The crude fluorinated aniline precipitated as a brown oil. The
brown oil was redissolved in 300 mL methylene chloride. The methylene
chloride was extracted 3 times with 0.1 M NaOH and 5 times with water
until neutral pH. The methylene chloride was dried over MgSO4 and
evaporated under reduced pressure. The isolated fluorinated aniline was
used without further purification.

[0186]Diazotation of 3-aminophenyl phosphonic acid: 13.6 g (78 mmol) of
3-aminophenyl phosphonic acid was dissolved in 20 mL HCl (conc.). The
reaction mixture was cooled to 0° C. A solution of 5.3 g of
NaNO2 in 10 mL water was added while keeping the temperature below
5° C. The mixture was stirred at 5° C. for 90 minutes,
before adding to the mixture described below.

[0187]Coupling of the diazonium salt: 20 g (36 mmol) of the fluorinated
aniline was dissolved in 76 mL acetic acid. 8.75 g of sodium acetate was
added and the mixture was cooled to 0° C. The solution of the
above prepared diazonium salt was added portion wise, while keeping the
pH of the mixture around pH=7. If the pH dropped below 7, NaOH was added
to the mixture until the pH was neutral. After the addition of the
diazonium salt was completed, the pH was raised further to pH 12. The
mixture was stirred for an additional hour at room temperature. The crude
contrast dye CD-3 precipitated form the medium and was isolated by
filtration. The isolated dye was treated with 200 mL methyl t.butyl ether
and dried. 6.9 g of contrast dye CD-3 was isolated.

Example 3

[0188]This example describes the synthesis of contrast dye CD-4.

##STR00060##

[0189]The carboxyphosphonic ester was prepared as described in example 18
of WO 96/19484 (PIERRE FABRE MEDICAMENT).

[0190]Esterification of N,N-bis-(2-hydroxyethyl)aniline: 21.9 g (006 mol)
of the carboxyphosphonic ester was dissolved in 150 mL methylene
chloride. 13.61 g (0.066 mol) of dicyclohexyl carbodiimide in 100 mL
methylene chloride was added and the mixture was stirred for 30 minutes
at room temperature. 5.43 g (0.03 mol) of N,N-bis-(2-hydroxyethyl)aniline
in 60 mL methylene chloride was added and the reaction was allowed to
continue for 30 minutes at room temperature. After stirring over night,
an additional 6.18 g of dicyclohexyl carbodiimide and 10.9 g of
carboxyphosphonic acid were added and the reaction was allowed to
continue at room temperature for an additional 30 minutes. The formed
dicyclohexyl urea was removed by filtration and the solvent was removed
under reduced pressure. The intermediate acylated aniline was isolated by
preparative column chromatography (eluent: ethyl acetate on Kromasil Si
60 A 10, 10 μm).

[0191]Cleavage of the phosphonate esters: 4.35 g (5 mmol) of the
intermediate anilino-phosphonate ester was dissolved in 40 mL methylene
chloride. 5 g of trimethylsilyl bromide was added and the reaction was
allowed to continue at room temperature for 2 hours. The solvent was
removed under reduced pressure and the residue was treated over night
with a mixture of 35 mL water, 30 mL methanol and 3 mL 2 N hydrochloric
acid. The solvent was evaporated under reduced pressure. The residue was
treated with a mixture of 40 mL methyl t.butyl ether and re-evaporated.
The isolated diphosphonic acid was used without further purification.

[0192]Diazotation of 2-amino-benzothiazole: 0.19 g (1.3 mmol) of
2-aminobenzothiazole was dissolved in 7.8 mL acetic acid and 2.6 mL
concentrated sulfuric acid. The mixture was cooled to 0° C. and a
solution of 98 mg of NaNO2 in 4 mL water was added. The reaction was
allowed to continue for 2 hours at 0° C.

[0193]Coupling of the diazonium salt: 1 g (1.3 mmol) of the diphosphonic
acid was dissolved in 25 mL acetic acid. 1.4 g of sodium acetate was
added. The diazotated 2-aminobenzothiazole was added to this mixture and
reaction was allowed to continue at room temperature for 3 hours. The
reaction mixture was poured into 150 mL water and acidified with 10 mL 6
N HCl. The mixture was extracted 3 times with 100 mL n.-butanol. The
pooled butanol extracts were dried over Na2SO4. The solvent was
removed under reduced pressure and contrast dye CD-4 was purified by
preparative column chromatography. (gradient elution form a mixture of
0.2 M ammonium acetate, adjusted to pH 8.7 with triethanol amine/methanol
90/10 to 100% MeOH on a Varian Mega BE-C18 column).

[0194]Contrast dye CD-4 was isolated as a mixture of diastereoisomers.

Example 4

[0195]This example describes the synthesis of contrast dye CD-5.

##STR00061##

[0196]4 g (11 mmol) of the carboxyphosphonic ester, prepared according to
WO 96/19484 (PF MEDICAMENT ET AL), was dissolved in 30 mL of dimethyl
acetamide. 2.14 g (15.2 mmol) of carbodiimidazole was added and the
reaction was allowed to continue for 30 minutes at room temperature. Then
1.62 g (5 mmol) of the diamino anthraquinone dye, prepared according to
EP 0154117 A (AMERICAN CYANAMID CO), in 80 mL of dimethyl acetamide was
added to the reaction mixture and the reaction was allowed to continue
for 16 hours at room temperature. The solvent was evaporated under
reduced pressure and the residue was dissolved in 250 mL of ethyl
acetate. The organic layer was washed twice with 250 mL of water, dried
over MgSO4 and evaporated under reduced pressure. The crude mixture
was dissolved in 100 mL of methylene chloride and treated with 3.06 g (20
mmol) of trimethylsilyl bromide. The reaction was allowed to continue for
5 hours at room temperature. The solvent was removed under reduced
pressure and 100 mL of methanol was added. Two drops of HCl (conc.) were
added and the reaction was allowed to continue for 14 hours at room
temperature. The solvent was removed under reduced pressure and the
residue was purified by preparative column chromatography, using a Varian
Mega BE-C18 flash column and a gradient elution from 50% methanol/50%
0.2M ammonium acetate, adjusted to pH 8.5 with triethanol amine, to pure
methanol. 1.35 g of the anthraquinone dye was isolated. Analysis showed
the presence of some residual esters and the product was treated again
with 2 g of trimethylsilyl bromide in 100 mL of methylene chloride. The
solvent was removed under reduced pressure and 100 mL of methanol was
added. The reaction was allowed to continue for 48 hours. The solvent was
removed under reduced pressure and the dye proved to be sufficiently pure
for evaluation.

Example 5

[0197]This example describes the synthesis of contrast dye CD-11.

##STR00062##

[0198]6.5 g (40 mmol) of 2-amino-4-chloro-thiazole-5-carbaldehyde was
dissolved in 50 mL of phosphoric acid. The mixture was cooled to
0° C. and 5.1 g (40 mmol) of nitrosylsulfuric acid was added while
the temperature was kept at 0° C.

[0199]7.5 g (45 mmol) of 2-hydroxyethyl-ethyl aniline was dissolved in a
mixture 100 g of ice and 50 mL of ethyl acetate. The diazotated thiazole
was added slowly to this mixture. The magenta dye was formed immediately.
500 mL of water was added to the reaction mixture and the dye
precipitated from the medium. The dye was isolated by filtration and
washed twice with water and dried. 6.8 g of the dye was isolated.

##STR00063##

[0200]24.6 g (50 mmol) of the fluorinated carboxylic acid was dissolved in
50 mL of ethyl acetate. 7 mL (50 mmol) of triethyl amine was added
dropwise followed by the addition of 4.4 g (25 mmol) of benzene
sulfochloride. The reaction was allowed to continue for 30 minutes at
room temperature. 9.7 g (25 mmol) of the in step 1 prepared azo dye,
dissolved in 50 mL of dimethyl acetamide, was added and the reaction was
allowed to continue for 16 hours at room temperature. After 16 hours 10
mol % of dimethylaminopyridine and an extra equivalent of the symmetrical
anhydride, prepared from the fluorinated carboxylic acid, triethyl amine
and benzenesulfochloride as described above, were added. The reaction was
allowed to continue for an extra 24 hours. The solvent was evaporated
under reduced pressure and the residue was dissolved in 100 mL of methyl
t.butyl ether. The organic layer was extracted twice with 100 mL of
water, dried over MgSO4 and evaporated under reduced pressure. The
fluorinated azo dye was isolated by preparative column chromatography on
a Varian Mega Bond Elut Si column, using ethyl acetate/hexane 50/50 as
eluent. 5.6 g of the dye was isolated.

##STR00064##

[0201]5 g (6 mmol) of the fluorinated azo dye was dissolved in 40 mL of
THF. 3 g (10 mmol) of tris(trimethylsilyl)phosphite was added and the
reaction was allowed to continue for 24 hours at room temperature. 1.4 mL
(10 mmol) of triethyl amine and 40 mL of methanol were added and the
reaction was allowed to continue for 24 hours at room temperature. The
solvents were removed under reduced pressure and the phosphonated dye was
isolated by preparative column chromatography on a Varian Mega BE-C18
flash column using methanol/water as eluent. 0.9 g of the dye was
isolated.

Example 6

[0202]This example describes the synthesis of contrast dyes CD-12 and
DYE-4. The contrast dye DYE-4 was synthesized for a comparative inkjet
ink having a contrast dye with two shorter aliphatic groups than the
contrast dye CD-12, i.e., ethyl instead of hexyl.

##STR00065##

[0203]The starting azo dye was prepared in a similar matter as described
above for contrast dye CD-11, using dihexyl aniline instead of
2-hydroxyethyl-ethyl-aniline.

[0204]4.4 g (10 mmol) of the azo dye was dissolved in 25 mL of THF. 3 g
(10 mmol) of tris(trimethylsilyl)phosphite was added and the reaction was
allowed to continue at room temperature for 6 hours. 10% excess of
tris(trimethylsilyl)phosphite was added and the reaction was allowed to
continue for an extra 12 hours. 50 mL of methanol and 10 mL of triethyl
amine were added and the reaction was allowed to continue at room
temperature for 12 hours. The reaction mixture was evaporated under
reduced pressure and the dye was isolated by preparative column
chromatography on a Varian Mega BE-C18 flash column, using a gradient
elution from 100% water to methanol/water 80/20. 4.4 g of the contrast
dye CD-12 was isolated.

##STR00066##

[0205]The starting azo dye was prepared in a similar matter as described
above for contrast dye CD-11, using diethyl aniline in stead of
2-hydroxyethyl-ethyl-aniline.

[0206]3.2 g (10 mmol) of the azo dye was dissolved in 25 mL of THF. 3 g
(10 mmol) tris(trimethylsilyl)phosphite was added and the reaction was
allowed to continue at room temperature for 16 hours. 60 mL of methanol
and 5 mL of triethyl amine were added and the reaction was allowed to
continue at room temperature for 12 hours. The solvent was removed under
reduced pressure and the residue was redissolved in 100 mL of water. The
aqueous layer was extracted twice with 100 mL of ethylacetate to remove
residual organic contaminants and the aqueous layer was evaporated under
reduced pressure. The residue was treated with 100 mL of hexane, isolated
by filtration and dried. 3.7 g of the contrast dye DYE-4 was isolated and
used for evaluation without further purification.

Example 7

[0207]This example illustrates that low molecular weight contrast dyes in
accordance with a preferred embodiment of the present invention not only
produce a clearly visible lithographic image that remains visible after
gumming, but are also suitable for printing in the absence of a
traditional oleophilizing agent.

Dyes for Comparative Inkjet Inks

[0208]The following dyes were used to prepare comparative inkjet inks:

##STR00067##

[0209]The contrast dye DYE-1 is widely commercially available. The
reference dyes DYE-2 and DYE-3 were prepared by conventional diazonium
chemistry as described in Vogel's Textbook of Practical Organic
Chemistry, fourth edition (Longman, London and New York). The synthesis
of DYE-4 is described above in Example 6.

Oleophilizing Compound OLEO-1

[0210]A first colorless oleophilizing compound contains two A groups and
two phosphonic acids groups (A groups) but no chromophore group.

##STR00068##

Synthesis of Oleophilizing Compound OLEO-1

##STR00069##

[0211]5.4 g (50 mmol) of p.-phenylene diamine and 15.3 mL (110 mmol) of
triethyl amine were dissolved in 200 mL of acetone. 47.9 g (125 mmol) of
(1-chlorocarbonyl-tridecyl)-phosphonic acid diethyl ester, prepared from
the carboxylic acid using thionyl chloride and dimethyl formamide as
catalyst, was dissolved in 100 acetone and added to the reaction mixture.
The reaction was allowed to continue for 3 hours at room temperature. An
extra 5.4 mL of triethyl amine was added and the reaction was allowed to
continue over night at room temperature. The precipitated triethyl amine
hydrochloride was removed by filtration and the acetone was evaporated
under reduced pressure. The crude product was purified by preparative
column chromatography, using methylene chloride/methanol 95/5 as eluent
on Kromasil Si 60 A 10 μm. 9.2 g of the intermediate was isolated as a
mixture of diastereoisomers.

[0212]9.2 g (11.5 mmol) of the purified intermediate was dissolved in 200
mL of methylene chloride. 10.6 g (69 mmol) of trimethylsilyl bromide was
added and the reaction was allowed to continue for 3 days at room
temperature. The solvent is removed under reduced pressure and 100 mL of
water and 1 mL of HCl 1N was added. The reaction was allowed to continue
for 24 hours at room temperature. The precipitated bis-phosphonic acid
was isolated by filtration, washed with 60 mL of water and dried. The
crude product was treated with 80 mL of methyl t.butyl ether, isolated by
filtration and dried. 6.8 g of the oleophilizing compound OLEO-1 was
isolated.

[0214]1.6 g (10 mmol) of hexamethylene diisocyanate and 2 g of
(4-aminobenzyl)-phosphonic acid diethyl ester chlorohydrate were added to
100 mL of ethyl acetate. 3.2 g of (4-aminobenzyl)-phosphonic acid diethyl
ester chlorohydrate was suspended in 50 mL of dimethyl acetamide and
added to the mixture. 2.8 mL of triethyl amine was added and all
compounds dissolved into the mixture. The reaction was allowed to
continue for 16 hours at room temperature. The crude intermediate
precipitated from the medium and was isolated by filtration. The
intermediate was purified by preparative column chromatography, using
methylene chloride/ethanol 93/7 as eluent on Kromasil Si 60 A 10 μm.
1.8 g (2.7 mmol) of the purified intermediate was dissolved in 40 mL of
methylene chloride and 2.5 g (16.2 mmol) of trimethylsilyl bromide was
added. The reaction was allowed to continue for several days at room
temperature. The solvent was removed under reduced pressure and 50 mL of
water and 5 mL of 1 N HCl were added. The reaction is allowed to continue
for 24 hours at room temperature. The crude bis-phosphonic acid was
isolated by filtration, treated with acetone and dried. 0.7 g of the
oleophilizing compound OLEO-2 was isolated.

Preparation of Inkjet Inks

[0215]All inkjet inks were prepared in the same manner to obtain a
composition as described in Table 3 for the comparative inkjet inks and
in Table 4 for the inventive inkjet inks.

[0216]First, the liquid carrier composition optimized for jetting
performance was prepared under stirring at room temperature by adding the
organic solvents, i.e., alkylene glycol(ether) and when applicable the
2-pyrolidone or isopropanol, to demineralized water. Stirring was
continued until a homogeneous solution was obtained. Then the low
molecular weight contrast dye was introduced into this carrier. Some
contrast dyes required addition of triethanolamine to improve the
solubility of the contrast dye in the liquid carrier (see table). In a
number of cases the inkjet ink composition was completed by addition of
an oleophilizing compound: Zonyl® FSE, or OLEO-2.

[0217]The comparative inkjet inks C-1 to C-7 and the inventive inkjet inks
I-1 to I-6 were evaluated on their image contrast and on their printing
properties. The results are shown in Table 5.

[0218]From Table 5, it can be seen that none of the comparative inkjet
inks C-1 to C-7 retained a visual contrast in the lithographic image
after a gumming treatment with the exception of comparative inkjet ink
C-5 which contained a contrast dye DYE-4 with aliphatic groups that are
too short for ink-uptake. On the other hand, the inventive inkjet inks
I-1 to I-6 all exhibited good visual contrast after gumming treatment.
The inventive inkjet inks I-1, I-2, I-5 and I-6 show that for these
contrast dyes the presence of an extra oleophilizing compound in the ink
was not required.

Example 8

[0219]This example describes the synthesis of contrast dye CPOL-1.

##STR00072## ##STR00073##

10.2 g of SMA1000P was dissolved in 50 mL of dimethyl acetamide. The
mixture was heated to 50° C. and a solution of 4.6 g of dodecyl
amine and 4.4 mL of diisopropyl ethyl amine was added dropwise. The
reaction was allowed to continue for 2 hours at 50° C. After 2
hours, a solution of 5.1 g of the blue black dye in 20 mL of dimethyl
acetamide and 5.5 mL of 5 N NaOH was added. The reaction was allowed to
continue for 16 hours at 60° C. The polymer was reactivated by
adding 5.2 g of dicyclohexyl carbodiimide to the reaction mixture. The
reaction was allowed to continue for 2 hours at 65° C. The polymer
was reactivated for a second time using 5.2 g of dicyclohexyl
carbodiimide. The reaction was allowed to continue for 2 hours at
65° C. The reaction mixture was allowed to cool down to room
temperature and the formed dicyclohexyl ureum was removed by filtration.
400 mL of water was added to the filtrate and an extra amount of
dicyclohexyl ureum precipitated. The precipitated ureum was removed by
filtration and the solvent was removed under reduced pressure. Contrast
dye CPOL-1 was isolated by preparative size exclusion chromatography
using a Sephadex G25 chromatographic phase, supplied by Pharmacia.

Example 9

[0220]This example describes the synthesis of contrast dye CPOL-6.

##STR00074##

8.2 g of SMA1000P was dissolved in 40 mL of dimethyl acetamide 4.2 g of
the anthraquinone dye (Hydroparabromesaure, supplied by Bayer AG) and 2
mL of triethyl amine were added. The reaction was allowed to continue at
room temperature for 16 hours. The reaction mixture was heated to
100° C. for an hour to drive the reaction to completion. After
cooling down to room temperature, 2.2 g of (1-aminopentyl)-phosphonic
acid diethyl ester was added and the reaction was allowed to continue for
one hour at room temperature, followed by the addition of 8 g of the
fluorinated amine. The reaction was allowed to continue for 16 hours at
room temperature. 15 g of trimethylsilyl bromide was added and the
reaction was allowed to continue for 24 hours at room temperature. 150 mL
of methanol was added and the reaction mixture was stirred for 16 hours
at room temperature. The polymer was precipitated in water, isolated by
filtration and dried. 31P-NMR clearly proved the presence of
deprotected phosphonic acids, while 19F-NMR proved the presence of
polymer bound fluorinated aliphatic chains.

Example 10

[0221]This example describes the synthesis of contrast dye CPOL-7.

##STR00075## ##STR00076##

4.0 g of SMA1000P was dissolved in 40 mL of dimethyl acetamide. 4.2 g of
the anthraquinone dye (Hydroparabromesaure, supplied by Bayer AG) and 1.4
mL of triethyl amine were added. The reaction was allowed to continue at
room temperature for 16 hours. The reaction mixture was heated to
100° C. for an hour to drive the reaction to completion. After
cooling down to room temperature 2.8 g of (1-aminododecyl)-phosphonic
acid diethyl ester (prepared according to the method described by Kudzin
et al., Synthesis 1980, 1028) and 1 g of triethyl amine were added and
the reaction was allowed to continue for 16 hours at room temperature.
12.4 g of trimethylsilyl bromide was added and the reaction was allowed
to continue 24 hours. 100 mL of methanol was added and the reaction was
allowed to continue for 48 hours. The polymer was precipitated in water
and was isolated by filtration. The crude polymer was purified using
preparative size exclusion chromatography on Sephadex G25 (Pharmacia). 5
g of the polymer was isolated. 31P-NMR proved the presence of mainly
uncleaved phosphonate esters. The polymer was redissolved in 40 mL of
dimethyl acetamide and treated with 10 mL of trimethylsilyl bromide. The
reaction was allowed to continue for 16 hours. 100 mL of methanol was
added and the reaction mixture was stirred for 16 hours. The polymer was
precipitated with water, isolated by filtration and dried. 31P-NMR
clearly proved the presence of fully deprotected phosphonic acids. The
experimental n/x/y ratio proved to be 50/25/25.

Example 11

[0222]This example illustrates that contrast dyes having a polymeric
backbone in accordance with a preferred embodiment of the present
invention not only produce a clearly visible lithographic image that
remains visible after gumming, but is suitable for printing in the
absence of a traditional oleophilizing agent.

Polymer POL-1 for Comparative Inkjet Ink

##STR00077##

[0223]10.2 g of SMA1000P was dissolved in 50 mL of dimethyl acetamide. 4.6
g of dodecyl amine and 4.4 mL of diispropyl ethyl amine were added
dropwise at 50° C. The reaction was allowed to continue at room
temperature for 2 hours. A solution of phosphoric acid
mono-(2-amino-ethyl)-ester in 10 mL of dimethyl acetamide, 7 mL of 5N
NaOH and 4.4 mL of diisopropyl ethyl amine was added at 50° C. The
reaction was allowed to continue for 16 hours at room temperature. A
small fraction of precipitated product was removed by filtration. 100 mL
of water was added to the filtrate and the mixture was acidified with 15
mL of 5M HCl. The polymer precipitated from the medium and was isolated
by filtration. The polymer was resuspended in 100 mL of water, isolated
by filtration and dried. 17.9 g of the polymer POL-1 was isolated. The
experimental n/x/y ratio based on 1H-NMR spectroscopy proved to be
56/19/25.

Polymer POL-1 for Comparative Inkjet Ink

##STR00078##

[0224]10.2 g of SMA1000P was dissolved in 50 mL of dimethyl acetamide. 4.6
g of dodecyl amine and 4.4 mL of diisopropyl ethyl amine were added
dropwise at 50° C. The reaction was allowed to continue at
50° C. for 2 hours. A solution of 4.3 g (3-aminophenyl)-phosphonic
acid in 10 mL of dimethyl acetamide, 4.4 mL of diispropyl ethyl amine and
5 mL of 5 N NaOH was added at 50° C. The reaction was allowed to
continue for 2 hours at 50° C. and further over night at room
temperature. 100 mL of water was added to the reaction mixture and the
mixture was acidified with 20 mL of 5N HCl. The polymer precipitated from
the medium and was isolated by filtration. The polymer was treated with
200 mL of water, isolated by filtration and treated with 150 mL of
isopropyl acetate. The undissolved residue was removed by filtration and
washed with 50 mL of ethylacetate. The filtrate was evaporated under
reduced pressure and the residue was treated with 200 mL of acetonitrile
for 1 hour. The polymer POL-2 was isolated by filtration, treated for a
second time with 150 mL of acetonitrile, isolated by filtration and
dried. 15.8 g of the polymer POL-2 was isolated. Th n/x/y ratio proved to
be 53/20/27 based on 1H-NMR-spectroscopy.

Preparation of Inkjet Inks

[0225]All inkjet inks were prepared in the same manner to obtain a
composition as described in Table 6 for the comparative inkjet inks C-8
and C-9 and for the inventive inkjet inks I-7 to I-10.

[0226]First, the liquid carrier composition optimized for jetting
performance was prepared under stirring at room temperature by adding the
organic solvents, i.e., propylene glycol and diethylene glycol, to
demineralized water. Stirring was continued until a homogeneous solution
was obtained. Then the contrast dye (DYE-5 for the comparative inkjet
inks C-8 and C-9 and CPOL-1, CPOL-6 or CPOL-7 for the inventive inkjet
inks I-7 to I-10) was introduced into this carrier. The contrast dye
DYE-5 required addition of triethanol amine to improve the solubility of
the contrast dye in the liquid carrier. The composition of the inventive
inkjet ink I-9 was completed by addition of Zonyl® FSE as an
oleophilizing compound.

[0227]The comparative inkjet inks C-8 and C-9 and the inventive inkjet
inks I-7 to I-10 were evaluated on their image contrast and printing
properties. The results are shown in Table 7.

[0228]From Table 7, it can be seen that the comparative inkjet inks C-8
and C-9 retained no visual contrast in the lithographic image after a
gumming treatment. On the other hand, the inventive inkjet inks I-7 to
I-10 all exhibited good visual contrast after gumming treatment, as well
as a rapid ink-uptake. The inventive inkjet inks I-7, I-8 and I-10 show
that for these contrast dyes the presence of an extra oleophilizing
compound, such as Zonyl® FSE in the inventive inkjet ink I-9, was not
required.

[0229]While preferred embodiments of the present invention have been
described above, it is to be understood that variations and modifications
will be apparent to those skilled in the art without departing the scope
and spirit of the present invention. The scope of the present invention,
therefore, is to be determined solely by the following claims.